The present invention comprises a new and distinct cultivar of Hydrangea plant known by the varietal name ‘Horpill’. The new variety was discovered in 1999 in a planned breeding program in Dresden, Germany. The purpose of the breeding program was to develop bicoloured Hydrangeas. The new variety is the result of a cross between ‘Moritzburg’ (female parent, unpatented) and ‘Nobuko’ (male parent). The inflorescence shape and foliage of the new variety are similar to its female parent, but ‘Moritzburg’ is not bicoloured. ‘Nobuko’ is bicoloured like the new variety, but differs from ‘Horpill’ in growth habit. The new variety was first asexually reproduced in 1999 via propagation by cuttings in Germany. The new variety has been trial and field tested in Germany and has been found to retain its distinctive characteristics and remain true to type through successive propagations.
The following traits distinguish ‘Horpill’ as a new and distinct cultivar from other Hydrangea varieties known to the breeder:                1. Bicoloured in nature;        2. Strong stems;        3. Dark foliage;        4. Compact growth habit;        5. Small leaves; and        6. Good root system.        
‘Horpill’ is similar to another Hydrangea variety, ‘Harlekin’ (unpatented), because they are both bicoloured with mop-heads and a compact growth habit. However, ‘Horpill’ differs from ‘Harlekin’ in stem quality, sterile flower shape, and root system characteristics.